Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * auth-scram.c
4 : * Server-side implementation of the SASL SCRAM-SHA-256 mechanism.
5 : *
6 : * See the following RFCs for more details:
7 : * - RFC 5802: https://tools.ietf.org/html/rfc5802
8 : * - RFC 5803: https://tools.ietf.org/html/rfc5803
9 : * - RFC 7677: https://tools.ietf.org/html/rfc7677
10 : *
11 : * Here are some differences:
12 : *
13 : * - Username from the authentication exchange is not used. The client
14 : * should send an empty string as the username.
15 : *
16 : * - If the password isn't valid UTF-8, or contains characters prohibited
17 : * by the SASLprep profile, we skip the SASLprep pre-processing and use
18 : * the raw bytes in calculating the hash.
19 : *
20 : * - If channel binding is used, the channel binding type is always
21 : * "tls-server-end-point". The spec says the default is "tls-unique"
22 : * (RFC 5802, section 6.1. Default Channel Binding), but there are some
23 : * problems with that. Firstly, not all SSL libraries provide an API to
24 : * get the TLS Finished message, required to use "tls-unique". Secondly,
25 : * "tls-unique" is not specified for TLS v1.3, and as of this writing,
26 : * it's not clear if there will be a replacement. We could support both
27 : * "tls-server-end-point" and "tls-unique", but for our use case,
28 : * "tls-unique" doesn't really have any advantages. The main advantage
29 : * of "tls-unique" would be that it works even if the server doesn't
30 : * have a certificate, but PostgreSQL requires a server certificate
31 : * whenever SSL is used, anyway.
32 : *
33 : *
34 : * The password stored in pg_authid consists of the iteration count, salt,
35 : * StoredKey and ServerKey.
36 : *
37 : * SASLprep usage
38 : * --------------
39 : *
40 : * One notable difference to the SCRAM specification is that while the
41 : * specification dictates that the password is in UTF-8, and prohibits
42 : * certain characters, we are more lenient. If the password isn't a valid
43 : * UTF-8 string, or contains prohibited characters, the raw bytes are used
44 : * to calculate the hash instead, without SASLprep processing. This is
45 : * because PostgreSQL supports other encodings too, and the encoding being
46 : * used during authentication is undefined (client_encoding isn't set until
47 : * after authentication). In effect, we try to interpret the password as
48 : * UTF-8 and apply SASLprep processing, but if it looks invalid, we assume
49 : * that it's in some other encoding.
50 : *
51 : * In the worst case, we misinterpret a password that's in a different
52 : * encoding as being Unicode, because it happens to consists entirely of
53 : * valid UTF-8 bytes, and we apply Unicode normalization to it. As long
54 : * as we do that consistently, that will not lead to failed logins.
55 : * Fortunately, the UTF-8 byte sequences that are ignored by SASLprep
56 : * don't correspond to any commonly used characters in any of the other
57 : * supported encodings, so it should not lead to any significant loss in
58 : * entropy, even if the normalization is incorrectly applied to a
59 : * non-UTF-8 password.
60 : *
61 : * Error handling
62 : * --------------
63 : *
64 : * Don't reveal user information to an unauthenticated client. We don't
65 : * want an attacker to be able to probe whether a particular username is
66 : * valid. In SCRAM, the server has to read the salt and iteration count
67 : * from the user's stored secret, and send it to the client. To avoid
68 : * revealing whether a user exists, when the client tries to authenticate
69 : * with a username that doesn't exist, or doesn't have a valid SCRAM
70 : * secret in pg_authid, we create a fake salt and iteration count
71 : * on-the-fly, and proceed with the authentication with that. In the end,
72 : * we'll reject the attempt, as if an incorrect password was given. When
73 : * we are performing a "mock" authentication, the 'doomed' flag in
74 : * scram_state is set.
75 : *
76 : * In the error messages, avoid printing strings from the client, unless
77 : * you check that they are pure ASCII. We don't want an unauthenticated
78 : * attacker to be able to spam the logs with characters that are not valid
79 : * to the encoding being used, whatever that is. We cannot avoid that in
80 : * general, after logging in, but let's do what we can here.
81 : *
82 : *
83 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
84 : * Portions Copyright (c) 1994, Regents of the University of California
85 : *
86 : * src/backend/libpq/auth-scram.c
87 : *
88 : *-------------------------------------------------------------------------
89 : */
90 : #include "postgres.h"
91 :
92 : #include <unistd.h>
93 :
94 : #include "access/xlog.h"
95 : #include "catalog/pg_control.h"
96 : #include "common/base64.h"
97 : #include "common/hmac.h"
98 : #include "common/saslprep.h"
99 : #include "common/scram-common.h"
100 : #include "common/sha2.h"
101 : #include "libpq/crypt.h"
102 : #include "libpq/sasl.h"
103 : #include "libpq/scram.h"
104 : #include "miscadmin.h"
105 :
106 : static void scram_get_mechanisms(Port *port, StringInfo buf);
107 : static void *scram_init(Port *port, const char *selected_mech,
108 : const char *shadow_pass);
109 : static int scram_exchange(void *opaq, const char *input, int inputlen,
110 : char **output, int *outputlen,
111 : const char **logdetail);
112 :
113 : /* Mechanism declaration */
114 : const pg_be_sasl_mech pg_be_scram_mech = {
115 : scram_get_mechanisms,
116 : scram_init,
117 : scram_exchange,
118 :
119 : PG_MAX_SASL_MESSAGE_LENGTH
120 : };
121 :
122 : /*
123 : * Status data for a SCRAM authentication exchange. This should be kept
124 : * internal to this file.
125 : */
126 : typedef enum
127 : {
128 : SCRAM_AUTH_INIT,
129 : SCRAM_AUTH_SALT_SENT,
130 : SCRAM_AUTH_FINISHED,
131 : } scram_state_enum;
132 :
133 : typedef struct
134 : {
135 : scram_state_enum state;
136 :
137 : Port *port;
138 : bool channel_binding_in_use;
139 :
140 : /* State data depending on the hash type */
141 : pg_cryptohash_type hash_type;
142 : int key_length;
143 :
144 : int iterations;
145 : char *salt; /* base64-encoded */
146 : uint8 ClientKey[SCRAM_MAX_KEY_LEN];
147 : uint8 StoredKey[SCRAM_MAX_KEY_LEN];
148 : uint8 ServerKey[SCRAM_MAX_KEY_LEN];
149 :
150 : /* Fields of the first message from client */
151 : char cbind_flag;
152 : char *client_first_message_bare;
153 : char *client_username;
154 : char *client_nonce;
155 :
156 : /* Fields from the last message from client */
157 : char *client_final_message_without_proof;
158 : char *client_final_nonce;
159 : uint8 ClientProof[SCRAM_MAX_KEY_LEN];
160 :
161 : /* Fields generated in the server */
162 : char *server_first_message;
163 : char *server_nonce;
164 :
165 : /*
166 : * If something goes wrong during the authentication, or we are performing
167 : * a "mock" authentication (see comments at top of file), the 'doomed'
168 : * flag is set. A reason for the failure, for the server log, is put in
169 : * 'logdetail'.
170 : */
171 : bool doomed;
172 : char *logdetail;
173 : } scram_state;
174 :
175 : static void read_client_first_message(scram_state *state, const char *input);
176 : static void read_client_final_message(scram_state *state, const char *input);
177 : static char *build_server_first_message(scram_state *state);
178 : static char *build_server_final_message(scram_state *state);
179 : static bool verify_client_proof(scram_state *state);
180 : static bool verify_final_nonce(scram_state *state);
181 : static void mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
182 : int *iterations, int *key_length, char **salt,
183 : uint8 *stored_key, uint8 *server_key);
184 : static bool is_scram_printable(char *p);
185 : static char *sanitize_char(char c);
186 : static char *sanitize_str(const char *s);
187 : static uint8 *scram_mock_salt(const char *username,
188 : pg_cryptohash_type hash_type,
189 : int key_length);
190 :
191 : /*
192 : * The number of iterations to use when generating new secrets.
193 : */
194 : int scram_sha_256_iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
195 :
196 : /*
197 : * Get a list of SASL mechanisms that this module supports.
198 : *
199 : * For the convenience of building the FE/BE packet that lists the
200 : * mechanisms, the names are appended to the given StringInfo buffer,
201 : * separated by '\0' bytes.
202 : */
203 : static void
204 134 : scram_get_mechanisms(Port *port, StringInfo buf)
205 : {
206 : /*
207 : * Advertise the mechanisms in decreasing order of importance. So the
208 : * channel-binding variants go first, if they are supported. Channel
209 : * binding is only supported with SSL.
210 : */
211 : #ifdef USE_SSL
212 134 : if (port->ssl_in_use)
213 : {
214 12 : appendStringInfoString(buf, SCRAM_SHA_256_PLUS_NAME);
215 12 : appendStringInfoChar(buf, '\0');
216 : }
217 : #endif
218 134 : appendStringInfoString(buf, SCRAM_SHA_256_NAME);
219 134 : appendStringInfoChar(buf, '\0');
220 134 : }
221 :
222 : /*
223 : * Initialize a new SCRAM authentication exchange status tracker. This
224 : * needs to be called before doing any exchange. It will be filled later
225 : * after the beginning of the exchange with authentication information.
226 : *
227 : * 'selected_mech' identifies the SASL mechanism that the client selected.
228 : * It should be one of the mechanisms that we support, as returned by
229 : * scram_get_mechanisms().
230 : *
231 : * 'shadow_pass' is the role's stored secret, from pg_authid.rolpassword.
232 : * The username was provided by the client in the startup message, and is
233 : * available in port->user_name. If 'shadow_pass' is NULL, we still perform
234 : * an authentication exchange, but it will fail, as if an incorrect password
235 : * was given.
236 : */
237 : static void *
238 112 : scram_init(Port *port, const char *selected_mech, const char *shadow_pass)
239 : {
240 : scram_state *state;
241 : bool got_secret;
242 :
243 112 : state = palloc0_object(scram_state);
244 112 : state->port = port;
245 112 : state->state = SCRAM_AUTH_INIT;
246 :
247 : /*
248 : * Parse the selected mechanism.
249 : *
250 : * Note that if we don't support channel binding, or if we're not using
251 : * SSL at all, we would not have advertised the PLUS variant in the first
252 : * place. If the client nevertheless tries to select it, it's a protocol
253 : * violation like selecting any other SASL mechanism we don't support.
254 : */
255 : #ifdef USE_SSL
256 112 : if (strcmp(selected_mech, SCRAM_SHA_256_PLUS_NAME) == 0 && port->ssl_in_use)
257 8 : state->channel_binding_in_use = true;
258 : else
259 : #endif
260 104 : if (strcmp(selected_mech, SCRAM_SHA_256_NAME) == 0)
261 104 : state->channel_binding_in_use = false;
262 : else
263 0 : ereport(ERROR,
264 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
265 : errmsg("client selected an invalid SASL authentication mechanism")));
266 :
267 : /*
268 : * Parse the stored secret.
269 : */
270 112 : if (shadow_pass)
271 : {
272 112 : int password_type = get_password_type(shadow_pass);
273 :
274 112 : if (password_type == PASSWORD_TYPE_SCRAM_SHA_256)
275 : {
276 110 : if (parse_scram_secret(shadow_pass, &state->iterations,
277 : &state->hash_type, &state->key_length,
278 : &state->salt,
279 110 : state->StoredKey,
280 110 : state->ServerKey))
281 110 : got_secret = true;
282 : else
283 : {
284 : /*
285 : * The password looked like a SCRAM secret, but could not be
286 : * parsed.
287 : */
288 0 : ereport(LOG,
289 : (errmsg("invalid SCRAM secret for user \"%s\"",
290 : state->port->user_name)));
291 0 : got_secret = false;
292 : }
293 : }
294 : else
295 : {
296 : /*
297 : * The user doesn't have SCRAM secret. (You cannot do SCRAM
298 : * authentication with an MD5 hash.)
299 : */
300 4 : state->logdetail = psprintf(_("User \"%s\" does not have a valid SCRAM secret."),
301 2 : state->port->user_name);
302 2 : got_secret = false;
303 : }
304 : }
305 : else
306 : {
307 : /*
308 : * The caller requested us to perform a dummy authentication. This is
309 : * considered normal, since the caller requested it, so don't set log
310 : * detail.
311 : */
312 0 : got_secret = false;
313 : }
314 :
315 : /*
316 : * If the user did not have a valid SCRAM secret, we still go through the
317 : * motions with a mock one, and fail as if the client supplied an
318 : * incorrect password. This is to avoid revealing information to an
319 : * attacker.
320 : */
321 112 : if (!got_secret)
322 : {
323 2 : mock_scram_secret(state->port->user_name, &state->hash_type,
324 : &state->iterations, &state->key_length,
325 : &state->salt,
326 2 : state->StoredKey, state->ServerKey);
327 2 : state->doomed = true;
328 : }
329 :
330 112 : return state;
331 : }
332 :
333 : /*
334 : * Continue a SCRAM authentication exchange.
335 : *
336 : * 'input' is the SCRAM payload sent by the client. On the first call,
337 : * 'input' contains the "Initial Client Response" that the client sent as
338 : * part of the SASLInitialResponse message, or NULL if no Initial Client
339 : * Response was given. (The SASL specification distinguishes between an
340 : * empty response and non-existing one.) On subsequent calls, 'input'
341 : * cannot be NULL. For convenience in this function, the caller must
342 : * ensure that there is a null terminator at input[inputlen].
343 : *
344 : * The next message to send to client is saved in 'output', for a length
345 : * of 'outputlen'. In the case of an error, optionally store a palloc'd
346 : * string at *logdetail that will be sent to the postmaster log (but not
347 : * the client).
348 : */
349 : static int
350 224 : scram_exchange(void *opaq, const char *input, int inputlen,
351 : char **output, int *outputlen, const char **logdetail)
352 : {
353 224 : scram_state *state = (scram_state *) opaq;
354 : int result;
355 :
356 224 : *output = NULL;
357 :
358 : /*
359 : * If the client didn't include an "Initial Client Response" in the
360 : * SASLInitialResponse message, send an empty challenge, to which the
361 : * client will respond with the same data that usually comes in the
362 : * Initial Client Response.
363 : */
364 224 : if (input == NULL)
365 : {
366 : Assert(state->state == SCRAM_AUTH_INIT);
367 :
368 0 : *output = pstrdup("");
369 0 : *outputlen = 0;
370 0 : return PG_SASL_EXCHANGE_CONTINUE;
371 : }
372 :
373 : /*
374 : * Check that the input length agrees with the string length of the input.
375 : * We can ignore inputlen after this.
376 : */
377 224 : if (inputlen == 0)
378 0 : ereport(ERROR,
379 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
380 : errmsg("malformed SCRAM message"),
381 : errdetail("The message is empty.")));
382 224 : if (inputlen != strlen(input))
383 0 : ereport(ERROR,
384 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
385 : errmsg("malformed SCRAM message"),
386 : errdetail("Message length does not match input length.")));
387 :
388 224 : switch (state->state)
389 : {
390 112 : case SCRAM_AUTH_INIT:
391 :
392 : /*
393 : * Initialization phase. Receive the first message from client
394 : * and be sure that it parsed correctly. Then send the challenge
395 : * to the client.
396 : */
397 112 : read_client_first_message(state, input);
398 :
399 : /* prepare message to send challenge */
400 112 : *output = build_server_first_message(state);
401 :
402 112 : state->state = SCRAM_AUTH_SALT_SENT;
403 112 : result = PG_SASL_EXCHANGE_CONTINUE;
404 112 : break;
405 :
406 112 : case SCRAM_AUTH_SALT_SENT:
407 :
408 : /*
409 : * Final phase for the server. Receive the response to the
410 : * challenge previously sent, verify, and let the client know that
411 : * everything went well (or not).
412 : */
413 112 : read_client_final_message(state, input);
414 :
415 112 : if (!verify_final_nonce(state))
416 0 : ereport(ERROR,
417 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
418 : errmsg("invalid SCRAM response"),
419 : errdetail("Nonce does not match.")));
420 :
421 : /*
422 : * Now check the final nonce and the client proof.
423 : *
424 : * If we performed a "mock" authentication that we knew would fail
425 : * from the get go, this is where we fail.
426 : *
427 : * The SCRAM specification includes an error code,
428 : * "invalid-proof", for authentication failure, but it also allows
429 : * erroring out in an application-specific way. We choose to do
430 : * the latter, so that the error message for invalid password is
431 : * the same for all authentication methods. The caller will call
432 : * ereport(), when we return PG_SASL_EXCHANGE_FAILURE with no
433 : * output.
434 : *
435 : * NB: the order of these checks is intentional. We calculate the
436 : * client proof even in a mock authentication, even though it's
437 : * bound to fail, to thwart timing attacks to determine if a role
438 : * with the given name exists or not.
439 : */
440 112 : if (!verify_client_proof(state) || state->doomed)
441 : {
442 10 : result = PG_SASL_EXCHANGE_FAILURE;
443 10 : break;
444 : }
445 :
446 : /* Build final message for client */
447 102 : *output = build_server_final_message(state);
448 :
449 : /* Success! */
450 102 : result = PG_SASL_EXCHANGE_SUCCESS;
451 102 : state->state = SCRAM_AUTH_FINISHED;
452 102 : break;
453 :
454 0 : default:
455 0 : elog(ERROR, "invalid SCRAM exchange state");
456 : result = PG_SASL_EXCHANGE_FAILURE;
457 : }
458 :
459 224 : if (result == PG_SASL_EXCHANGE_FAILURE && state->logdetail && logdetail)
460 2 : *logdetail = state->logdetail;
461 :
462 224 : if (*output)
463 214 : *outputlen = strlen(*output);
464 :
465 224 : if (result == PG_SASL_EXCHANGE_SUCCESS && state->state == SCRAM_AUTH_FINISHED)
466 : {
467 102 : memcpy(MyProcPort->scram_ClientKey, state->ClientKey, sizeof(MyProcPort->scram_ClientKey));
468 102 : memcpy(MyProcPort->scram_ServerKey, state->ServerKey, sizeof(MyProcPort->scram_ServerKey));
469 102 : MyProcPort->has_scram_keys = true;
470 : }
471 :
472 224 : return result;
473 : }
474 :
475 : /*
476 : * Construct a SCRAM secret, for storing in pg_authid.rolpassword.
477 : *
478 : * The result is palloc'd, so caller is responsible for freeing it.
479 : */
480 : char *
481 106 : pg_be_scram_build_secret(const char *password)
482 : {
483 : char *prep_password;
484 : pg_saslprep_rc rc;
485 : uint8 saltbuf[SCRAM_DEFAULT_SALT_LEN];
486 : char *result;
487 106 : const char *errstr = NULL;
488 :
489 : /*
490 : * Normalize the password with SASLprep. If that doesn't work, because
491 : * the password isn't valid UTF-8 or contains prohibited characters, just
492 : * proceed with the original password. (See comments at top of file.)
493 : */
494 106 : rc = pg_saslprep(password, &prep_password);
495 106 : if (rc == SASLPREP_SUCCESS)
496 104 : password = (const char *) prep_password;
497 :
498 : /* Generate random salt */
499 106 : if (!pg_strong_random(saltbuf, SCRAM_DEFAULT_SALT_LEN))
500 0 : ereport(ERROR,
501 : (errcode(ERRCODE_INTERNAL_ERROR),
502 : errmsg("could not generate random salt")));
503 :
504 106 : result = scram_build_secret(PG_SHA256, SCRAM_SHA_256_KEY_LEN,
505 : saltbuf, SCRAM_DEFAULT_SALT_LEN,
506 : scram_sha_256_iterations, password,
507 : &errstr);
508 :
509 106 : if (prep_password)
510 104 : pfree(prep_password);
511 :
512 106 : return result;
513 : }
514 :
515 : /*
516 : * Verify a plaintext password against a SCRAM secret. This is used when
517 : * performing plaintext password authentication for a user that has a SCRAM
518 : * secret stored in pg_authid.
519 : */
520 : bool
521 54 : scram_verify_plain_password(const char *username, const char *password,
522 : const char *secret)
523 : {
524 : char *encoded_salt;
525 : uint8 *salt;
526 : int saltlen;
527 : int iterations;
528 54 : int key_length = 0;
529 : pg_cryptohash_type hash_type;
530 : uint8 salted_password[SCRAM_MAX_KEY_LEN];
531 : uint8 stored_key[SCRAM_MAX_KEY_LEN];
532 : uint8 server_key[SCRAM_MAX_KEY_LEN];
533 : uint8 computed_key[SCRAM_MAX_KEY_LEN];
534 : char *prep_password;
535 : pg_saslprep_rc rc;
536 54 : const char *errstr = NULL;
537 :
538 54 : if (!parse_scram_secret(secret, &iterations, &hash_type, &key_length,
539 : &encoded_salt, stored_key, server_key))
540 : {
541 : /*
542 : * The password looked like a SCRAM secret, but could not be parsed.
543 : */
544 0 : ereport(LOG,
545 : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
546 0 : return false;
547 : }
548 :
549 54 : saltlen = pg_b64_dec_len(strlen(encoded_salt));
550 54 : salt = palloc(saltlen);
551 54 : saltlen = pg_b64_decode(encoded_salt, strlen(encoded_salt), salt,
552 : saltlen);
553 54 : if (saltlen < 0)
554 : {
555 0 : ereport(LOG,
556 : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
557 0 : return false;
558 : }
559 :
560 : /* Normalize the password */
561 54 : rc = pg_saslprep(password, &prep_password);
562 54 : if (rc == SASLPREP_SUCCESS)
563 54 : password = prep_password;
564 :
565 : /* Compute Server Key based on the user-supplied plaintext password */
566 54 : if (scram_SaltedPassword(password, hash_type, key_length,
567 : salt, saltlen, iterations,
568 54 : salted_password, &errstr) < 0 ||
569 54 : scram_ServerKey(salted_password, hash_type, key_length,
570 : computed_key, &errstr) < 0)
571 : {
572 0 : elog(ERROR, "could not compute server key: %s", errstr);
573 : }
574 :
575 54 : if (prep_password)
576 54 : pfree(prep_password);
577 :
578 : /*
579 : * Compare the secret's Server Key with the one computed from the
580 : * user-supplied password.
581 : */
582 54 : return memcmp(computed_key, server_key, key_length) == 0;
583 : }
584 :
585 :
586 : /*
587 : * Parse and validate format of given SCRAM secret.
588 : *
589 : * On success, the iteration count, salt, stored key, and server key are
590 : * extracted from the secret, and returned to the caller. For 'stored_key'
591 : * and 'server_key', the caller must pass pre-allocated buffers of size
592 : * SCRAM_MAX_KEY_LEN. Salt is returned as a base64-encoded, null-terminated
593 : * string. The buffer for the salt is palloc'd by this function.
594 : *
595 : * Returns true if the SCRAM secret has been parsed, and false otherwise.
596 : */
597 : bool
598 876 : parse_scram_secret(const char *secret, int *iterations,
599 : pg_cryptohash_type *hash_type, int *key_length,
600 : char **salt, uint8 *stored_key, uint8 *server_key)
601 : {
602 : char *v;
603 : char *p;
604 : char *scheme_str;
605 : char *salt_str;
606 : char *iterations_str;
607 : char *storedkey_str;
608 : char *serverkey_str;
609 : int decoded_len;
610 : uint8 *decoded_salt_buf;
611 : uint8 *decoded_stored_buf;
612 : uint8 *decoded_server_buf;
613 :
614 : /*
615 : * The secret is of form:
616 : *
617 : * SCRAM-SHA-256$<iterations>:<salt>$<storedkey>:<serverkey>
618 : */
619 876 : v = pstrdup(secret);
620 876 : scheme_str = strsep(&v, "$");
621 876 : if (v == NULL)
622 230 : goto invalid_secret;
623 646 : iterations_str = strsep(&v, ":");
624 646 : if (v == NULL)
625 12 : goto invalid_secret;
626 634 : salt_str = strsep(&v, "$");
627 634 : if (v == NULL)
628 0 : goto invalid_secret;
629 634 : storedkey_str = strsep(&v, ":");
630 634 : if (v == NULL)
631 0 : goto invalid_secret;
632 634 : serverkey_str = v;
633 :
634 : /* Parse the fields */
635 634 : if (strcmp(scheme_str, "SCRAM-SHA-256") != 0)
636 0 : goto invalid_secret;
637 634 : *hash_type = PG_SHA256;
638 634 : *key_length = SCRAM_SHA_256_KEY_LEN;
639 :
640 634 : errno = 0;
641 634 : *iterations = strtol(iterations_str, &p, 10);
642 634 : if (*p || errno != 0)
643 0 : goto invalid_secret;
644 :
645 : /*
646 : * Verify that the salt is in Base64-encoded format, by decoding it,
647 : * although we return the encoded version to the caller.
648 : */
649 634 : decoded_len = pg_b64_dec_len(strlen(salt_str));
650 634 : decoded_salt_buf = palloc(decoded_len);
651 634 : decoded_len = pg_b64_decode(salt_str, strlen(salt_str),
652 : decoded_salt_buf, decoded_len);
653 634 : if (decoded_len < 0)
654 0 : goto invalid_secret;
655 634 : *salt = pstrdup(salt_str);
656 :
657 : /*
658 : * Decode StoredKey and ServerKey.
659 : */
660 634 : decoded_len = pg_b64_dec_len(strlen(storedkey_str));
661 634 : decoded_stored_buf = palloc(decoded_len);
662 634 : decoded_len = pg_b64_decode(storedkey_str, strlen(storedkey_str),
663 : decoded_stored_buf, decoded_len);
664 634 : if (decoded_len != *key_length)
665 12 : goto invalid_secret;
666 622 : memcpy(stored_key, decoded_stored_buf, *key_length);
667 :
668 622 : decoded_len = pg_b64_dec_len(strlen(serverkey_str));
669 622 : decoded_server_buf = palloc(decoded_len);
670 622 : decoded_len = pg_b64_decode(serverkey_str, strlen(serverkey_str),
671 : decoded_server_buf, decoded_len);
672 622 : if (decoded_len != *key_length)
673 12 : goto invalid_secret;
674 610 : memcpy(server_key, decoded_server_buf, *key_length);
675 :
676 610 : return true;
677 :
678 266 : invalid_secret:
679 266 : *salt = NULL;
680 266 : return false;
681 : }
682 :
683 : /*
684 : * Generate plausible SCRAM secret parameters for mock authentication.
685 : *
686 : * In a normal authentication, these are extracted from the secret
687 : * stored in the server. This function generates values that look
688 : * realistic, for when there is no stored secret, using SCRAM-SHA-256.
689 : *
690 : * Like in parse_scram_secret(), for 'stored_key' and 'server_key', the
691 : * caller must pass pre-allocated buffers of size SCRAM_MAX_KEY_LEN, and
692 : * the buffer for the salt is palloc'd by this function.
693 : */
694 : static void
695 2 : mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
696 : int *iterations, int *key_length, char **salt,
697 : uint8 *stored_key, uint8 *server_key)
698 : {
699 : uint8 *raw_salt;
700 : char *encoded_salt;
701 : int encoded_len;
702 :
703 : /* Enforce the use of SHA-256, which would be realistic enough */
704 2 : *hash_type = PG_SHA256;
705 2 : *key_length = SCRAM_SHA_256_KEY_LEN;
706 :
707 : /*
708 : * Generate deterministic salt.
709 : *
710 : * Note that we cannot reveal any information to an attacker here so the
711 : * error messages need to remain generic. This should never fail anyway
712 : * as the salt generated for mock authentication uses the cluster's nonce
713 : * value.
714 : */
715 2 : raw_salt = scram_mock_salt(username, *hash_type, *key_length);
716 2 : if (raw_salt == NULL)
717 0 : elog(ERROR, "could not encode salt");
718 :
719 2 : encoded_len = pg_b64_enc_len(SCRAM_DEFAULT_SALT_LEN);
720 : /* don't forget the zero-terminator */
721 2 : encoded_salt = (char *) palloc(encoded_len + 1);
722 2 : encoded_len = pg_b64_encode(raw_salt, SCRAM_DEFAULT_SALT_LEN, encoded_salt,
723 : encoded_len);
724 :
725 2 : if (encoded_len < 0)
726 0 : elog(ERROR, "could not encode salt");
727 2 : encoded_salt[encoded_len] = '\0';
728 :
729 2 : *salt = encoded_salt;
730 2 : *iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
731 :
732 : /* StoredKey and ServerKey are not used in a doomed authentication */
733 2 : memset(stored_key, 0, SCRAM_MAX_KEY_LEN);
734 2 : memset(server_key, 0, SCRAM_MAX_KEY_LEN);
735 2 : }
736 :
737 : /*
738 : * Read the value in a given SCRAM exchange message for given attribute.
739 : */
740 : static char *
741 456 : read_attr_value(char **input, char attr)
742 : {
743 456 : char *begin = *input;
744 : char *end;
745 :
746 456 : if (*begin != attr)
747 0 : ereport(ERROR,
748 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
749 : errmsg("malformed SCRAM message"),
750 : errdetail("Expected attribute \"%c\" but found \"%s\".",
751 : attr, sanitize_char(*begin))));
752 456 : begin++;
753 :
754 456 : if (*begin != '=')
755 0 : ereport(ERROR,
756 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
757 : errmsg("malformed SCRAM message"),
758 : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
759 456 : begin++;
760 :
761 456 : end = begin;
762 9704 : while (*end && *end != ',')
763 9248 : end++;
764 :
765 456 : if (*end)
766 : {
767 344 : *end = '\0';
768 344 : *input = end + 1;
769 : }
770 : else
771 112 : *input = end;
772 :
773 456 : return begin;
774 : }
775 :
776 : static bool
777 112 : is_scram_printable(char *p)
778 : {
779 : /*------
780 : * Printable characters, as defined by SCRAM spec: (RFC 5802)
781 : *
782 : * printable = %x21-2B / %x2D-7E
783 : * ;; Printable ASCII except ",".
784 : * ;; Note that any "printable" is also
785 : * ;; a valid "value".
786 : *------
787 : */
788 2800 : for (; *p; p++)
789 : {
790 2688 : if (*p < 0x21 || *p > 0x7E || *p == 0x2C /* comma */ )
791 0 : return false;
792 : }
793 112 : return true;
794 : }
795 :
796 : /*
797 : * Convert an arbitrary byte to printable form. For error messages.
798 : *
799 : * If it's a printable ASCII character, print it as a single character.
800 : * otherwise, print it in hex.
801 : *
802 : * The returned pointer points to a static buffer.
803 : */
804 : static char *
805 0 : sanitize_char(char c)
806 : {
807 : static char buf[5];
808 :
809 0 : if (c >= 0x21 && c <= 0x7E)
810 0 : snprintf(buf, sizeof(buf), "'%c'", c);
811 : else
812 0 : snprintf(buf, sizeof(buf), "0x%02x", (unsigned char) c);
813 0 : return buf;
814 : }
815 :
816 : /*
817 : * Convert an arbitrary string to printable form, for error messages.
818 : *
819 : * Anything that's not a printable ASCII character is replaced with
820 : * '?', and the string is truncated at 30 characters.
821 : *
822 : * The returned pointer points to a static buffer.
823 : */
824 : static char *
825 0 : sanitize_str(const char *s)
826 : {
827 : static char buf[30 + 1];
828 : int i;
829 :
830 0 : for (i = 0; i < sizeof(buf) - 1; i++)
831 : {
832 0 : char c = s[i];
833 :
834 0 : if (c == '\0')
835 0 : break;
836 :
837 0 : if (c >= 0x21 && c <= 0x7E)
838 0 : buf[i] = c;
839 : else
840 0 : buf[i] = '?';
841 : }
842 0 : buf[i] = '\0';
843 0 : return buf;
844 : }
845 :
846 : /*
847 : * Read the next attribute and value in a SCRAM exchange message.
848 : *
849 : * The attribute character is set in *attr_p, the attribute value is the
850 : * return value.
851 : */
852 : static char *
853 112 : read_any_attr(char **input, char *attr_p)
854 : {
855 112 : char *begin = *input;
856 : char *end;
857 112 : char attr = *begin;
858 :
859 112 : if (attr == '\0')
860 0 : ereport(ERROR,
861 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
862 : errmsg("malformed SCRAM message"),
863 : errdetail("Attribute expected, but found end of string.")));
864 :
865 : /*------
866 : * attr-val = ALPHA "=" value
867 : * ;; Generic syntax of any attribute sent
868 : * ;; by server or client
869 : *------
870 : */
871 112 : if (!((attr >= 'A' && attr <= 'Z') ||
872 112 : (attr >= 'a' && attr <= 'z')))
873 0 : ereport(ERROR,
874 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
875 : errmsg("malformed SCRAM message"),
876 : errdetail("Attribute expected, but found invalid character \"%s\".",
877 : sanitize_char(attr))));
878 112 : if (attr_p)
879 112 : *attr_p = attr;
880 112 : begin++;
881 :
882 112 : if (*begin != '=')
883 0 : ereport(ERROR,
884 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
885 : errmsg("malformed SCRAM message"),
886 : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
887 112 : begin++;
888 :
889 112 : end = begin;
890 5040 : while (*end && *end != ',')
891 4928 : end++;
892 :
893 112 : if (*end)
894 : {
895 0 : *end = '\0';
896 0 : *input = end + 1;
897 : }
898 : else
899 112 : *input = end;
900 :
901 112 : return begin;
902 : }
903 :
904 : /*
905 : * Read and parse the first message from client in the context of a SCRAM
906 : * authentication exchange message.
907 : *
908 : * At this stage, any errors will be reported directly with ereport(ERROR).
909 : */
910 : static void
911 112 : read_client_first_message(scram_state *state, const char *input)
912 : {
913 112 : char *p = pstrdup(input);
914 : char *channel_binding_type;
915 :
916 :
917 : /*------
918 : * The syntax for the client-first-message is: (RFC 5802)
919 : *
920 : * saslname = 1*(value-safe-char / "=2C" / "=3D")
921 : * ;; Conforms to <value>.
922 : *
923 : * authzid = "a=" saslname
924 : * ;; Protocol specific.
925 : *
926 : * cb-name = 1*(ALPHA / DIGIT / "." / "-")
927 : * ;; See RFC 5056, Section 7.
928 : * ;; E.g., "tls-server-end-point" or
929 : * ;; "tls-unique".
930 : *
931 : * gs2-cbind-flag = ("p=" cb-name) / "n" / "y"
932 : * ;; "n" -> client doesn't support channel binding.
933 : * ;; "y" -> client does support channel binding
934 : * ;; but thinks the server does not.
935 : * ;; "p" -> client requires channel binding.
936 : * ;; The selected channel binding follows "p=".
937 : *
938 : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
939 : * ;; GS2 header for SCRAM
940 : * ;; (the actual GS2 header includes an optional
941 : * ;; flag to indicate that the GSS mechanism is not
942 : * ;; "standard", but since SCRAM is "standard", we
943 : * ;; don't include that flag).
944 : *
945 : * username = "n=" saslname
946 : * ;; Usernames are prepared using SASLprep.
947 : *
948 : * reserved-mext = "m=" 1*(value-char)
949 : * ;; Reserved for signaling mandatory extensions.
950 : * ;; The exact syntax will be defined in
951 : * ;; the future.
952 : *
953 : * nonce = "r=" c-nonce [s-nonce]
954 : * ;; Second part provided by server.
955 : *
956 : * c-nonce = printable
957 : *
958 : * client-first-message-bare =
959 : * [reserved-mext ","]
960 : * username "," nonce ["," extensions]
961 : *
962 : * client-first-message =
963 : * gs2-header client-first-message-bare
964 : *
965 : * For example:
966 : * n,,n=user,r=fyko+d2lbbFgONRv9qkxdawL
967 : *
968 : * The "n,," in the beginning means that the client doesn't support
969 : * channel binding, and no authzid is given. "n=user" is the username.
970 : * However, in PostgreSQL the username is sent in the startup packet, and
971 : * the username in the SCRAM exchange is ignored. libpq always sends it
972 : * as an empty string. The last part, "r=fyko+d2lbbFgONRv9qkxdawL" is
973 : * the client nonce.
974 : *------
975 : */
976 :
977 : /*
978 : * Read gs2-cbind-flag. (For details see also RFC 5802 Section 6 "Channel
979 : * Binding".)
980 : */
981 112 : state->cbind_flag = *p;
982 112 : switch (*p)
983 : {
984 104 : case 'n':
985 :
986 : /*
987 : * The client does not support channel binding or has simply
988 : * decided to not use it. In that case just let it go.
989 : */
990 104 : if (state->channel_binding_in_use)
991 0 : ereport(ERROR,
992 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
993 : errmsg("malformed SCRAM message"),
994 : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
995 :
996 104 : p++;
997 104 : if (*p != ',')
998 0 : ereport(ERROR,
999 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1000 : errmsg("malformed SCRAM message"),
1001 : errdetail("Comma expected, but found character \"%s\".",
1002 : sanitize_char(*p))));
1003 104 : p++;
1004 104 : break;
1005 0 : case 'y':
1006 :
1007 : /*
1008 : * The client supports channel binding and thinks that the server
1009 : * does not. In this case, the server must fail authentication if
1010 : * it supports channel binding.
1011 : */
1012 0 : if (state->channel_binding_in_use)
1013 0 : ereport(ERROR,
1014 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1015 : errmsg("malformed SCRAM message"),
1016 : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
1017 :
1018 : #ifdef USE_SSL
1019 0 : if (state->port->ssl_in_use)
1020 0 : ereport(ERROR,
1021 : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1022 : errmsg("SCRAM channel binding negotiation error"),
1023 : errdetail("The client supports SCRAM channel binding but thinks the server does not. "
1024 : "However, this server does support channel binding.")));
1025 : #endif
1026 0 : p++;
1027 0 : if (*p != ',')
1028 0 : ereport(ERROR,
1029 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1030 : errmsg("malformed SCRAM message"),
1031 : errdetail("Comma expected, but found character \"%s\".",
1032 : sanitize_char(*p))));
1033 0 : p++;
1034 0 : break;
1035 8 : case 'p':
1036 :
1037 : /*
1038 : * The client requires channel binding. Channel binding type
1039 : * follows, e.g., "p=tls-server-end-point".
1040 : */
1041 8 : if (!state->channel_binding_in_use)
1042 0 : ereport(ERROR,
1043 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1044 : errmsg("malformed SCRAM message"),
1045 : errdetail("The client selected SCRAM-SHA-256 without channel binding, but the SCRAM message includes channel binding data.")));
1046 :
1047 8 : channel_binding_type = read_attr_value(&p, 'p');
1048 :
1049 : /*
1050 : * The only channel binding type we support is
1051 : * tls-server-end-point.
1052 : */
1053 8 : if (strcmp(channel_binding_type, "tls-server-end-point") != 0)
1054 0 : ereport(ERROR,
1055 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1056 : errmsg("unsupported SCRAM channel-binding type \"%s\"",
1057 : sanitize_str(channel_binding_type))));
1058 8 : break;
1059 0 : default:
1060 0 : ereport(ERROR,
1061 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1062 : errmsg("malformed SCRAM message"),
1063 : errdetail("Unexpected channel-binding flag \"%s\".",
1064 : sanitize_char(*p))));
1065 : }
1066 :
1067 : /*
1068 : * Forbid optional authzid (authorization identity). We don't support it.
1069 : */
1070 112 : if (*p == 'a')
1071 0 : ereport(ERROR,
1072 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1073 : errmsg("client uses authorization identity, but it is not supported")));
1074 112 : if (*p != ',')
1075 0 : ereport(ERROR,
1076 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1077 : errmsg("malformed SCRAM message"),
1078 : errdetail("Unexpected attribute \"%s\" in client-first-message.",
1079 : sanitize_char(*p))));
1080 112 : p++;
1081 :
1082 112 : state->client_first_message_bare = pstrdup(p);
1083 :
1084 : /*
1085 : * Any mandatory extensions would go here. We don't support any.
1086 : *
1087 : * RFC 5802 specifies error code "e=extensions-not-supported" for this,
1088 : * but it can only be sent in the server-final message. We prefer to fail
1089 : * immediately (which the RFC also allows).
1090 : */
1091 112 : if (*p == 'm')
1092 0 : ereport(ERROR,
1093 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1094 : errmsg("client requires an unsupported SCRAM extension")));
1095 :
1096 : /*
1097 : * Read username. Note: this is ignored. We use the username from the
1098 : * startup message instead, still it is kept around if provided as it
1099 : * proves to be useful for debugging purposes.
1100 : */
1101 112 : state->client_username = read_attr_value(&p, 'n');
1102 :
1103 : /* read nonce and check that it is made of only printable characters */
1104 112 : state->client_nonce = read_attr_value(&p, 'r');
1105 112 : if (!is_scram_printable(state->client_nonce))
1106 0 : ereport(ERROR,
1107 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1108 : errmsg("non-printable characters in SCRAM nonce")));
1109 :
1110 : /*
1111 : * There can be any number of optional extensions after this. We don't
1112 : * support any extensions, so ignore them.
1113 : */
1114 112 : while (*p != '\0')
1115 0 : read_any_attr(&p, NULL);
1116 :
1117 : /* success! */
1118 112 : }
1119 :
1120 : /*
1121 : * Verify the final nonce contained in the last message received from
1122 : * client in an exchange.
1123 : */
1124 : static bool
1125 112 : verify_final_nonce(scram_state *state)
1126 : {
1127 112 : int client_nonce_len = strlen(state->client_nonce);
1128 112 : int server_nonce_len = strlen(state->server_nonce);
1129 112 : int final_nonce_len = strlen(state->client_final_nonce);
1130 :
1131 112 : if (final_nonce_len != client_nonce_len + server_nonce_len)
1132 0 : return false;
1133 112 : if (memcmp(state->client_final_nonce, state->client_nonce, client_nonce_len) != 0)
1134 0 : return false;
1135 112 : if (memcmp(state->client_final_nonce + client_nonce_len, state->server_nonce, server_nonce_len) != 0)
1136 0 : return false;
1137 :
1138 112 : return true;
1139 : }
1140 :
1141 : /*
1142 : * Verify the client proof contained in the last message received from
1143 : * client in an exchange. Returns true if the verification is a success,
1144 : * or false for a failure.
1145 : */
1146 : static bool
1147 112 : verify_client_proof(scram_state *state)
1148 : {
1149 : uint8 ClientSignature[SCRAM_MAX_KEY_LEN];
1150 : uint8 client_StoredKey[SCRAM_MAX_KEY_LEN];
1151 112 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1152 : int i;
1153 112 : const char *errstr = NULL;
1154 :
1155 : /*
1156 : * Calculate ClientSignature. Note that we don't log directly a failure
1157 : * here even when processing the calculations as this could involve a mock
1158 : * authentication.
1159 : */
1160 224 : if (pg_hmac_init(ctx, state->StoredKey, state->key_length) < 0 ||
1161 112 : pg_hmac_update(ctx,
1162 112 : (uint8 *) state->client_first_message_bare,
1163 224 : strlen(state->client_first_message_bare)) < 0 ||
1164 224 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1165 112 : pg_hmac_update(ctx,
1166 112 : (uint8 *) state->server_first_message,
1167 224 : strlen(state->server_first_message)) < 0 ||
1168 224 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1169 112 : pg_hmac_update(ctx,
1170 112 : (uint8 *) state->client_final_message_without_proof,
1171 224 : strlen(state->client_final_message_without_proof)) < 0 ||
1172 112 : pg_hmac_final(ctx, ClientSignature, state->key_length) < 0)
1173 : {
1174 0 : elog(ERROR, "could not calculate client signature: %s",
1175 : pg_hmac_error(ctx));
1176 : }
1177 :
1178 112 : pg_hmac_free(ctx);
1179 :
1180 : /* Extract the ClientKey that the client calculated from the proof */
1181 3696 : for (i = 0; i < state->key_length; i++)
1182 3584 : state->ClientKey[i] = state->ClientProof[i] ^ ClientSignature[i];
1183 :
1184 : /* Hash it one more time, and compare with StoredKey */
1185 112 : if (scram_H(state->ClientKey, state->hash_type, state->key_length,
1186 : client_StoredKey, &errstr) < 0)
1187 0 : elog(ERROR, "could not hash stored key: %s", errstr);
1188 :
1189 112 : if (memcmp(client_StoredKey, state->StoredKey, state->key_length) != 0)
1190 10 : return false;
1191 :
1192 102 : return true;
1193 : }
1194 :
1195 : /*
1196 : * Build the first server-side message sent to the client in a SCRAM
1197 : * communication exchange.
1198 : */
1199 : static char *
1200 112 : build_server_first_message(scram_state *state)
1201 : {
1202 : /*------
1203 : * The syntax for the server-first-message is: (RFC 5802)
1204 : *
1205 : * server-first-message =
1206 : * [reserved-mext ","] nonce "," salt ","
1207 : * iteration-count ["," extensions]
1208 : *
1209 : * nonce = "r=" c-nonce [s-nonce]
1210 : * ;; Second part provided by server.
1211 : *
1212 : * c-nonce = printable
1213 : *
1214 : * s-nonce = printable
1215 : *
1216 : * salt = "s=" base64
1217 : *
1218 : * iteration-count = "i=" posit-number
1219 : * ;; A positive number.
1220 : *
1221 : * Example:
1222 : *
1223 : * r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,s=QSXCR+Q6sek8bf92,i=4096
1224 : *------
1225 : */
1226 :
1227 : /*
1228 : * Per the spec, the nonce may consist of any printable ASCII characters.
1229 : * For convenience, however, we don't use the whole range available,
1230 : * rather, we generate some random bytes, and base64 encode them.
1231 : */
1232 : uint8 raw_nonce[SCRAM_RAW_NONCE_LEN];
1233 : int encoded_len;
1234 :
1235 112 : if (!pg_strong_random(raw_nonce, SCRAM_RAW_NONCE_LEN))
1236 0 : ereport(ERROR,
1237 : (errcode(ERRCODE_INTERNAL_ERROR),
1238 : errmsg("could not generate random nonce")));
1239 :
1240 112 : encoded_len = pg_b64_enc_len(SCRAM_RAW_NONCE_LEN);
1241 : /* don't forget the zero-terminator */
1242 112 : state->server_nonce = palloc(encoded_len + 1);
1243 112 : encoded_len = pg_b64_encode(raw_nonce, SCRAM_RAW_NONCE_LEN,
1244 : state->server_nonce, encoded_len);
1245 112 : if (encoded_len < 0)
1246 0 : ereport(ERROR,
1247 : (errcode(ERRCODE_INTERNAL_ERROR),
1248 : errmsg("could not encode random nonce")));
1249 112 : state->server_nonce[encoded_len] = '\0';
1250 :
1251 112 : state->server_first_message =
1252 112 : psprintf("r=%s%s,s=%s,i=%d",
1253 : state->client_nonce, state->server_nonce,
1254 : state->salt, state->iterations);
1255 :
1256 112 : return pstrdup(state->server_first_message);
1257 : }
1258 :
1259 :
1260 : /*
1261 : * Read and parse the final message received from client.
1262 : */
1263 : static void
1264 112 : read_client_final_message(scram_state *state, const char *input)
1265 : {
1266 : char attr;
1267 : char *channel_binding;
1268 : char *value;
1269 : char *begin,
1270 : *proof;
1271 : char *p;
1272 : uint8 *client_proof;
1273 : int client_proof_len;
1274 :
1275 112 : begin = p = pstrdup(input);
1276 :
1277 : /*------
1278 : * The syntax for the server-first-message is: (RFC 5802)
1279 : *
1280 : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
1281 : * ;; GS2 header for SCRAM
1282 : * ;; (the actual GS2 header includes an optional
1283 : * ;; flag to indicate that the GSS mechanism is not
1284 : * ;; "standard", but since SCRAM is "standard", we
1285 : * ;; don't include that flag).
1286 : *
1287 : * cbind-input = gs2-header [ cbind-data ]
1288 : * ;; cbind-data MUST be present for
1289 : * ;; gs2-cbind-flag of "p" and MUST be absent
1290 : * ;; for "y" or "n".
1291 : *
1292 : * channel-binding = "c=" base64
1293 : * ;; base64 encoding of cbind-input.
1294 : *
1295 : * proof = "p=" base64
1296 : *
1297 : * client-final-message-without-proof =
1298 : * channel-binding "," nonce [","
1299 : * extensions]
1300 : *
1301 : * client-final-message =
1302 : * client-final-message-without-proof "," proof
1303 : *------
1304 : */
1305 :
1306 : /*
1307 : * Read channel binding. This repeats the channel-binding flags and is
1308 : * then followed by the actual binding data depending on the type.
1309 : */
1310 112 : channel_binding = read_attr_value(&p, 'c');
1311 112 : if (state->channel_binding_in_use)
1312 : {
1313 : #ifdef USE_SSL
1314 8 : const char *cbind_data = NULL;
1315 8 : size_t cbind_data_len = 0;
1316 : size_t cbind_header_len;
1317 : char *cbind_input;
1318 : size_t cbind_input_len;
1319 : char *b64_message;
1320 : int b64_message_len;
1321 :
1322 : Assert(state->cbind_flag == 'p');
1323 :
1324 : /* Fetch hash data of server's SSL certificate */
1325 8 : cbind_data = be_tls_get_certificate_hash(state->port,
1326 : &cbind_data_len);
1327 :
1328 : /* should not happen */
1329 8 : if (cbind_data == NULL || cbind_data_len == 0)
1330 0 : elog(ERROR, "could not get server certificate hash");
1331 :
1332 8 : cbind_header_len = strlen("p=tls-server-end-point,,"); /* p=type,, */
1333 8 : cbind_input_len = cbind_header_len + cbind_data_len;
1334 8 : cbind_input = palloc(cbind_input_len);
1335 8 : snprintf(cbind_input, cbind_input_len, "p=tls-server-end-point,,");
1336 8 : memcpy(cbind_input + cbind_header_len, cbind_data, cbind_data_len);
1337 :
1338 8 : b64_message_len = pg_b64_enc_len(cbind_input_len);
1339 : /* don't forget the zero-terminator */
1340 8 : b64_message = palloc(b64_message_len + 1);
1341 8 : b64_message_len = pg_b64_encode((uint8 *) cbind_input, cbind_input_len,
1342 : b64_message, b64_message_len);
1343 8 : if (b64_message_len < 0)
1344 0 : elog(ERROR, "could not encode channel binding data");
1345 8 : b64_message[b64_message_len] = '\0';
1346 :
1347 : /*
1348 : * Compare the value sent by the client with the value expected by the
1349 : * server.
1350 : */
1351 8 : if (strcmp(channel_binding, b64_message) != 0)
1352 0 : ereport(ERROR,
1353 : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1354 : errmsg("SCRAM channel binding check failed")));
1355 : #else
1356 : /* shouldn't happen, because we checked this earlier already */
1357 : elog(ERROR, "channel binding not supported by this build");
1358 : #endif
1359 : }
1360 : else
1361 : {
1362 : /*
1363 : * If we are not using channel binding, the binding data is expected
1364 : * to always be "biws", which is "n,," base64-encoded, or "eSws",
1365 : * which is "y,,". We also have to check whether the flag is the same
1366 : * one that the client originally sent.
1367 : */
1368 104 : if (!(strcmp(channel_binding, "biws") == 0 && state->cbind_flag == 'n') &&
1369 0 : !(strcmp(channel_binding, "eSws") == 0 && state->cbind_flag == 'y'))
1370 0 : ereport(ERROR,
1371 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1372 : errmsg("unexpected SCRAM channel-binding attribute in client-final-message")));
1373 : }
1374 :
1375 112 : state->client_final_nonce = read_attr_value(&p, 'r');
1376 :
1377 : /* ignore optional extensions, read until we find "p" attribute */
1378 : do
1379 : {
1380 112 : proof = p - 1;
1381 112 : value = read_any_attr(&p, &attr);
1382 112 : } while (attr != 'p');
1383 :
1384 112 : client_proof_len = pg_b64_dec_len(strlen(value));
1385 112 : client_proof = palloc(client_proof_len);
1386 112 : if (pg_b64_decode(value, strlen(value), client_proof,
1387 112 : client_proof_len) != state->key_length)
1388 0 : ereport(ERROR,
1389 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1390 : errmsg("malformed SCRAM message"),
1391 : errdetail("Malformed proof in client-final-message.")));
1392 112 : memcpy(state->ClientProof, client_proof, state->key_length);
1393 112 : pfree(client_proof);
1394 :
1395 112 : if (*p != '\0')
1396 0 : ereport(ERROR,
1397 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1398 : errmsg("malformed SCRAM message"),
1399 : errdetail("Garbage found at the end of client-final-message.")));
1400 :
1401 112 : state->client_final_message_without_proof = palloc(proof - begin + 1);
1402 112 : memcpy(state->client_final_message_without_proof, input, proof - begin);
1403 112 : state->client_final_message_without_proof[proof - begin] = '\0';
1404 112 : }
1405 :
1406 : /*
1407 : * Build the final server-side message of an exchange.
1408 : */
1409 : static char *
1410 102 : build_server_final_message(scram_state *state)
1411 : {
1412 : uint8 ServerSignature[SCRAM_MAX_KEY_LEN];
1413 : char *server_signature_base64;
1414 : int siglen;
1415 102 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1416 :
1417 : /* calculate ServerSignature */
1418 204 : if (pg_hmac_init(ctx, state->ServerKey, state->key_length) < 0 ||
1419 102 : pg_hmac_update(ctx,
1420 102 : (uint8 *) state->client_first_message_bare,
1421 204 : strlen(state->client_first_message_bare)) < 0 ||
1422 204 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1423 102 : pg_hmac_update(ctx,
1424 102 : (uint8 *) state->server_first_message,
1425 204 : strlen(state->server_first_message)) < 0 ||
1426 204 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1427 102 : pg_hmac_update(ctx,
1428 102 : (uint8 *) state->client_final_message_without_proof,
1429 204 : strlen(state->client_final_message_without_proof)) < 0 ||
1430 102 : pg_hmac_final(ctx, ServerSignature, state->key_length) < 0)
1431 : {
1432 0 : elog(ERROR, "could not calculate server signature: %s",
1433 : pg_hmac_error(ctx));
1434 : }
1435 :
1436 102 : pg_hmac_free(ctx);
1437 :
1438 102 : siglen = pg_b64_enc_len(state->key_length);
1439 : /* don't forget the zero-terminator */
1440 102 : server_signature_base64 = palloc(siglen + 1);
1441 102 : siglen = pg_b64_encode(ServerSignature,
1442 : state->key_length, server_signature_base64,
1443 : siglen);
1444 102 : if (siglen < 0)
1445 0 : elog(ERROR, "could not encode server signature");
1446 102 : server_signature_base64[siglen] = '\0';
1447 :
1448 : /*------
1449 : * The syntax for the server-final-message is: (RFC 5802)
1450 : *
1451 : * verifier = "v=" base64
1452 : * ;; base-64 encoded ServerSignature.
1453 : *
1454 : * server-final-message = (server-error / verifier)
1455 : * ["," extensions]
1456 : *
1457 : *------
1458 : */
1459 102 : return psprintf("v=%s", server_signature_base64);
1460 : }
1461 :
1462 :
1463 : /*
1464 : * Deterministically generate salt for mock authentication, using a SHA256
1465 : * hash based on the username and a cluster-level secret key. Returns a
1466 : * pointer to a static buffer of size SCRAM_DEFAULT_SALT_LEN, or NULL.
1467 : */
1468 : static uint8 *
1469 2 : scram_mock_salt(const char *username, pg_cryptohash_type hash_type,
1470 : int key_length)
1471 : {
1472 : pg_cryptohash_ctx *ctx;
1473 : static uint8 sha_digest[SCRAM_MAX_KEY_LEN];
1474 2 : char *mock_auth_nonce = GetMockAuthenticationNonce();
1475 :
1476 : /*
1477 : * Generate salt using a SHA256 hash of the username and the cluster's
1478 : * mock authentication nonce. (This works as long as the salt length is
1479 : * not larger than the SHA256 digest length. If the salt is smaller, the
1480 : * caller will just ignore the extra data.)
1481 : */
1482 : StaticAssertDecl(PG_SHA256_DIGEST_LENGTH >= SCRAM_DEFAULT_SALT_LEN,
1483 : "salt length greater than SHA256 digest length");
1484 :
1485 : /*
1486 : * This may be worth refreshing if support for more hash methods is\
1487 : * added.
1488 : */
1489 : Assert(hash_type == PG_SHA256);
1490 :
1491 2 : ctx = pg_cryptohash_create(hash_type);
1492 4 : if (pg_cryptohash_init(ctx) < 0 ||
1493 4 : pg_cryptohash_update(ctx, (uint8 *) username, strlen(username)) < 0 ||
1494 4 : pg_cryptohash_update(ctx, (uint8 *) mock_auth_nonce, MOCK_AUTH_NONCE_LEN) < 0 ||
1495 2 : pg_cryptohash_final(ctx, sha_digest, key_length) < 0)
1496 : {
1497 0 : pg_cryptohash_free(ctx);
1498 0 : return NULL;
1499 : }
1500 2 : pg_cryptohash_free(ctx);
1501 :
1502 2 : return sha_digest;
1503 : }
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